Composite material, brazing alloys and process of manufacture



Sept. 26, 1961 H. s. MOORE ET AL 9 2 COMPOSITE MATERIAL, BRAZING ALLOYS AND PROCESS OF MANUFACTURE Filed Sept. 20, 1954 Hidhi@ COMPOS TE MATER L BRAZENG AL QYS i u PROCESS OF MANUFACTURE HghS. Moore and Vincent F. Procopio, Pittslield, Mass., assignors to General Electrie ompay,'a corporation of New York Filed Sept. 20, 1954, Ser. No. %7,262

6 Claims. ((31. 29-43! tanium or zirconium, or combinations' thereof. scaling materials containing titanium are* already known, this substance having been found to' make an extremely intirnate bond withieeramic surfaces. 'In preyiousbonding pracesses, this substance ,has been utilied in its free or `metallict form as tita'nium, or in' the form ofttanium hydride which, in' the sealing operation', dissoeiates to cleposit metallic titanium on .the surface to which it is applied; In its' elementai or nelyrdivided state, ttanium is ex tremely active and is readily converted tothe oxide, which prevents the formationof an effective ceramio-to-mtal seal. This has required the use of .a relatively pure hydrogen or other non naidizing atmosphere for the brazing process. Furthermore, intprevious methods of making coranic-to metel seals usingtitanium it has been ncessary to carry out the process in a plurality of steps which resulted in elaborate, time-consuming and expensive op erations. For example, in known processes a titaniumontainiug'materal is first applied to a surface of a ceramic' article to be bonded to a metal, and then a'series ofivmetal layers are applied, such as by painting,-s`prayins, leetroplating and the like, ever th initial deposit of &taninet-containing material, the metal article or meny ber tobe bonded then `being weld'ed o-` otherwise joined to the outermnst metal layer. in many cases the titaniurn alioy materials used heretofore werefound to be unsat isfactory as brazing alloys, since they were quite brittle andhard to work and apply efectively to the surfaees to ba sealed or metallized. i i .i i

It is an object, therefore, oi the present invention to provide a brazing alloy which overcomes the above-mentio'ned disadvantages. i ;It is a further objectof the present invention to pro Vide, a simplified process of making Fluid-fight,` strongly adherent ceramic-to-rnetal and cerarnc-to-ceramic seals. li is another object of the present invention to provide an improved hrazing o'soldering' all oy'for making ef fective ceramic-to-metal and ceramic-to ceramic seals.

It is a further object of the present invention to provide a joint structure using the above improved soldejring alloy. i

A- brazng alloy material of'the present invention, by way of example, may be composed of a fusihle alloy consisting essentially of titanium, copper, silver and a c m t h g a a in Point lower h n the em g m t le i' he a ey It has'b en o d, i ojrdan e with he inventiomm t ea i a du le lo melting point metal which is of an exceptional value in ice 2 the present' brazing alloy. Among othernotable advantages, lead was found to greatly aid the flow of the molt'en alloy composition to which it was added, thereby enabling the' alloy to more eiiectivelyfunetion 'as a soldering material.

In this connection the expressions brazing" and "soldering" as used hei-ein are intended to refet' to the same operation, which involves the process of uniti'ng bodi'e s using a fusible material at a temperature above the molting point .of the latter material.

Features of the invention' which are believed noyel re set forth in particular in the appended claims. The vaution itself, howe ver together with further objc'cts and :advantages thei-cof may be better understood from the following description taken in connection with the aeco-mpanying drawing in' which:

' FIG. 1 is a sectionalview of a ceramicnsulating bushing: joined to metallic members in accordance with the present invention;

FIG. 2 is an exploded View of the assembly shown-' in FIG. 1 showing the Component parts thereof; and

FIG B is a View of an insulatingceramic bushing pre'- vided with a metallizng coating in accordance witl'th invention. Referring now to the drawing, and particularly to FIGS. l and 2, there is shown a ceratnic'bushing 2 iiiserted lcosely into an aperture 1' in a metal capacitor cover I or the like, the bushing 2 having a channel 2' through which a wire may pass to be onnected to terminal 3.

In making the joint 4 between .ceramic bushing 2 and metal cover 1, a brazing ring 4a (see FIGi 2) ispr'efer -ably first arranged at the junction of the bu'shing and the cover, the brazing ring being composed of the 'alloy material having a composition more fully described heretinafter. The thus assembled parte are placed ina 'furnace mufile in a non oxidizing atmosphere, such as in hydrogen or a dissociated annnonia atmosphere, and hoat:- ed to a temperature above the' melting point of the'alloy, buttbelow the melting points of metal cover 1. At such temperature, the brazing ring da melts, and by virtue of the lead Component therein and the capilla-y flow and wetting action which is promoted thereby, the molten alloy fiows well along the adjoining surfaces of both the metal cover l and ce'amo bushing 2 to form a strong herm'etic `seat joining the bushing to the' cover; The fluid-fight joint formed thereby has been found totesult from a' Chemical bond between the alloy material, and the bonded surfaces which is stronger than the ce'- ramic itself. The, assembly .can be moved into the cool'- ing zone of the fumace immediately after melting occurs, the time for both scaling and cooling depending on' the mass of the assembly. Of particular significance'in this procedure is the fact that the entire brazing operation takes place in one step with the use of only one brazing material, thus considerably simplifying the bond ing operation.

i Joint 5 between terminal 3, which may beof brass'` composition, and the top of. cer-amic bushing 2 may be' forrned in a manner similar to that of seal 4,witl1 the ass'en bledtparts being simultaneously heated to braze the ter'- minal G 'to bushing 2. However, it will be generally found convenient or desirable to initially apply' thebr'az ing ring sa' only to the buhing and metallize the letter with the brazingtalloy at the fusing temperature. 'In uch procedure the lead Component of the' brazing alloy lilgewse promotes wettng of the ceramic surface to en hance the intimate bond between the titanium or the alloy and the ceramic. The propotion of lead in the alloy used in this procedure is preferably less than that. used in making joint 4, so as to confine the flow of the brazing material more or less to the area at the top of bushing 2, since less spreading of the allo y is desired in' into' thesurface of terminal 3 to'thereby: form ai strong :ceramic-t-mettl seal, as in the previously described -procedures'. e r e ;EIG Bp illustrates -a ceramic'bushing which is provded with a metallzed brazing coating '7 having a com'- V ;position in accordance with the present 'invention. The `material which forms'coating 1 may b'e a finely-divided ;form of :the alloy rnetals described herein, .thepowdered V ;alloy or metalmixtures being Suspended' ina fugitive yehicle to faclitate application' ofthe alloy as a coat.- ing to the cerarnic surface. 'Such carrier materials may includejvarnsh, lacquer; celluloseacetate, .cellulose ;znitrate and the like. The lsuspended alloy` material 'i's then appliedinitially to the bushing in any suitable man ;ner and heated in a non-oxidizing atmosphere 'above the melting point of thei alloy to thereby'form 'a metallized coating 7 onthe bushing. `Thereafter,-whentdesired,lthe :metallized bushing 6 may be inserted' into' an` 'aperture or recess of a supporting plate such as cover '1,"and by heating .theassembly to a* suitable temperature, a portion .of th metallized coating will flow into the adjoning surface, of, the-supporting plate and will forma strong 'hermetie -ceramic-to-metal seal "between the supporting .plate and the lbushing. -Ifdesired, insteadfof applying coating'7 'by means of a suspension of the brazing alloy -finely` divided' forn,', the'` metallized coating may be .formed 'merely by placing ajbrazng ring at the desired ,position on` the bushing and fusing the brazing ring' to the' ;bushing under suitable heat in 'a non-oxidizing atmos- .phere. Either process will produce equally satisfactory and effective bonding results. 7 5,? In forming the'present alloy for use in solid form, the metal componentstof the present alloy preferably are first' finely divided to a size corresponding to the order of 325 mesh. The powders are mechanically mixed in proportions according to thedesired properties, and are then pressed into the desired form of the appropriate size,` such as in a ring, rod, ribbon or other suitable form. These pressed metal forms are then sintered at about 100 C. below the melting point of the alloy in ahydrogen atmosphere.` The incorporation of a ductile metal such as lead in the alloy, in accordance with the invention, facilitates the shaping of the solid alloy into desired form, which makes the alloy more convenient to apply to the area where the joint or seal is to be made. e The present brazing alloy may be efiectively used for V metallizng or scaling ceramicmaterials of a great variety,

including the materials mentioned above in defining the expression "c'eramic" as used heren.- The surfaces of the ceramicsto 'be bonded can be smooth, glazed, or rough and need not be clean in order'to be effectively bonded by the present alloy.

The metals which may be suitably directly bonded to ceramics by the use of the present brazing alloys should, of course, be those having a melting point higher than the particular composition 'of brazing alloy used. Such metals include, but are not limited to, steel, iron, copper, brass, nickel and alloysthereof. i

While the present brazing alloy will find particular use for direct ceramic-to-metal seals where the metal is of* 'a higher melting point than the, alloy, the present alloy is also adapted foruse in bonding metals having lower melting points, such as' aluminum and magnesium. Bodies made of such metals may be joined to 'ceramics provided with a metal brazing coating of the present invention merely by brazing the metal, eg., aluminum, ,to

the metal coating using known commercial aluminum brazing material, which melts 50 C. below the melting point of aluminum, in knownbrazing methods. Such a process is much simplerthan previous methods, which have required considerably more complicated operations to eifectivcly join aluninum to a cerann'c, such as by casting the aluminum onto a ceramicsurface which-has i been provided with separatesealingand soldering lay ers; Using thepresent process, an alunn'nu-n ,capacitor casin'g,fo`r example, can be' hermetically joined 'to a i bushing metallized in accordance with the invention.

The composition of'the present brazing, alloy will vary depending on such factors as the desired melting point, the extent of flow of the alloy, the degree of wetting of the surfaces to which the alloy is applied, the degree 'of ductility of the formed alloy or finished joint,

the particular surfaces to be bonded, and otherfactors. 'In general, the brazing' alloys of the present invention willhavea :melting point ranging between 650 C.-1100'? C. The particular components of the brazing alloy may be divided into three, groups. In `the first group there is preferably included titanium or zirc'onium and alloys oi',

combinations ,thei-cof. These metals, particularly titanium, ditfuse into the ceramc surfaces to be bonded and due to their reactive nature comhine chemically therewith .to forman'intmate bond with the ceramc member to which they are applied.

'The second group includes a ductile metal of comparatively lowlmeltng point which serves to increase the flow of 'the alloy and its wetting efiect, and of this' group lead has been found to be by far the most 'eiectiva Other metals whichmay be suitably used instead of'lead include zinc, bismuth, cadmium, indium, and tin, and

combnations'and alloys thereof.

The third group of Components includes such metals as Copper, silver, 'and nickel and combinations andalloys thereof, these metals serving to provide the main structure or body of the brazed jointandimpat the necessary strength thereto. Copper in particular is effective for wetting'steel. contributes to wetting of the copper..

: The amount of lead in the brazing 'alloy will vary ber tween 10-85 byweght depending largely'on'the-degree of ductility and extentof flow desired in the alloy. In amounts over 30%, the lead serves to provide flexibility in the resulting joint, such as in a butt joint between a ceramic and a metal where the difference in the co'- efficients of expansion-of the bonded materials is relatvely great. The use of lead in the alloyproduces marked improvements in the brazing alloy as well as the brazing process using the same, and provides nu'- merous advantages.- t For example, the replacement of the titanium in the brazing material by lead not only allows a reduction in cost of the alloy, but also reduces` the brittleness of the finished joint caused by excessive amounts of titanium. Further, the lead makes the alloy ductile enough to be shaped into desired form for convenient brazing operations, eg., shaped into ring form as shown in the drawing. Also, lead lowers the melting point of the alloy so as to allow working with metals It of lower melting points than heretofore possible. increases the flow of the alloy in the brazing operation, and by wetting the surfaces to be bonded'induces capillary action causing the alloy to flow into the joint. A particularly significant function of the lead is its protection of the highly active titanium in the alloy from oxidation which may result in a less satsfactory bond; Hence, the heating of the alloy in the brazing process may be carried .out in a poorer non-oxidizing atmosphere, such as in ordinary line hydrogen, than is nec,.- essary in brazing operations where titanium hydrde, for example, is used in the brazing alloy. This allows con: tinuous brazing operations to be carried on, if desired;

In the brazing alloy about 240% of ttanium s'prei, u erably used, with 5% being usually of particul r pret-,

In scaling to copper hardware, silver i p flow of the brazed metal.

&comes ,ther-titanium. While these substances have proved extremel'y eifective in the present alloy composition in producing excellent ceramie-to-metal sealsand are preferred,` there are also indications thats tantalum and niobium may give comparable results.

, 'Iheremainder of the alloy, as mentioned above, is preferably constitutedby copper, silver, nickel or com binatons or alloys thereof. Copper is preferably used i in the range of -8'5%, silver in the range of 5-85%,

and nickel in the range of 5-20% The following table sets forth several specific compositions of the present brazing alloys, but it should be understood that these compositions are given by way of illustration only and are not to be interpreted as limiting the scope of the invention in any way, since other and different compositions may be etfectively used depending on the particular results sought or materials to be bonded.

COMPOSITONS IN PERCENT BY WEIGHT A certain amount of flexiblity is possible within an alloy composition. 'For example, in' composition II, which is preferred as a general purpose material, the lead content can be varied from to 30% with a corresponding alteration of the copper content. Changes within these limits do not appreciably alterthe melting point, which is in agreement with the Copper-lead phase diagram. The eifect of such changes is to vary the degree of Bonding takes place but little or no flow is found with 15% lead and increasing lead up to 30% produces a corresponding increase in flow. Ac-

i cordngly, an alloy having compositionII would be selected where good flow is desired, whereas an alloy having composition I would be chosen where the amount of flow of the alloy is to be restricted. Alloy V would be selected for use where a particularly low melting point is desired, while alloy VI would serve best where a high i melting point alloy is necessary.

the present invention has been mainly described with` respect to ceramic-to-metal seals provided by the pres- 'ent brazing alloy,' other types of seals such as ceramicto-ceramic and even netal-to-metal joints may be eiec`- tively achieved with the use of the present compositions, since the alloy has been found to be generally useful in directly bonding materials of a great variety so long as they are of melting points higher than the alloys. Also, while the invention has been shown and described with 'reference to joining ceramic bushings to a capacitor cover and the application of' a metallized coating to a ceramic bushing, it is obvious that other objects and bodies could be similarly joined or metallized preparatory to joining without departing from the scope of the invention. Further, instead of metallizing a ceramic prior to joining it to a metal as described above, the metal may first be metallized before it is joined to the ceramic, if desired.

The present inventon lends itself for use in a variety of applications, and among these might be mentioned the hetallizing of glass or other ceramic plates to form with either pressed or wet process porcclains, steatite and similar ceramics; and the manufacture of doublerwalled evacuated devices such as window penes and vacuum containers. Other applications and uses will oeeur to those skilled ,in the art.

What we claim as new and desire to secure by Letters Patent of the United States is: i

l. A soldering material composed of a fusible alloy consisting essentially of about 4-10% by weight of a metal selected from the group consisting of titanium and zirconium and combinatons and alloys thereof; about 1o-s5% of lead; and the remainder a metal selected from the group consisting of copper, silver, and nickel and combirations and alloys thereof.

2. A joint structure comprising a cerarnic member and a metal member joined by including a bonding material formed from a fusible alloy consisting essentially of about 2-l0% by Weight of a metal selected from the group consisting of titanium and zirconium and combinetions and alloys thereof; about 10-85% of lead; and the remainder a metal selected from the group consisting of coppersilver, and nickel and combinations and alloys thereof.

3. A joint structure comprisng a ceramic member and a metal member joined by a bonding material formed from a fusible alloy consisting essentially of about 2-10% by weight of a metal selected from the group consisting of titanium and zirconium and combinations and alloys thereof; about 10-85 of a ductle metal selected from the group consisting of lead, zine, bismuth, cadmium, indium, and tin, and combinations and alloys thereof; and the remainder a metal selected from the group consisti'ng of Copper, silver, and nickel, and combinations and'alloys thereof. e

4. A joint structure ccmprising ceramic bodies joined together by a soldering material composed of a fusible alloy consisting essentially of about 2-`l0% by weight of a metal selected from the group consisting of titanium and zirconium and combinations and alloys thereof; about 10-85 of a ductle metal selected from the group consistirg of lead, Zinc, -bismuth, cadmium, indium, and tin, and combinations and alloys thereof; and the remainder a metal selected from the group consisting of copper, silver, and nickel, and combinations and alloys thereof.

5. The method of bonding 'a ceramic to an aluminum member which comprises metallizing the surface of the ceramic With a fusible alloy consisting essentially of 2-l0% by Weight of a metal selected from the group consisting of titanium and zirconium and combinatons and alloys thereof; about lil-% of a ductle metal selected from the group consisting of lead, zinc, bismuth, cadmium, indium, and tin, andcombinations and alloys thereof; and the remainder a metal selected from the group consisting of copper, silver and nickel, and combinations and alloys thereof; and brazing the aluminum member to the fusible alloy thus boncled to the ceratnic surface, thereby forming a tightly adherent hermetic ceramic-to-aluminum seal.

6. The method of bonding a ceramic to an aluminum member which comprises metal-lizing the surface of the ceramic with a fusible alloy consisting essentially of about 2-10% by weight of a metal selected from the group consisting of titanium and zirconium and combinations and alloys thereo-f, about 10-85% of lead, and the remainder a metal selected from the group consisting of copper, silver, and nickel, and combinations and alloys tlereof; and brazing the aluminum member to the `fusible alloy thue bonded to the ceramic surface, thereby forming a tightly adherent hermetic ceramic-to-alumirm seal.

(References on following page) V UNITED STATES PATENT'OFFICE CERTIFICATE OF CORRECTION ate t 3,001,29

column llrlel 2 after ."by' strike out "i ncluding-;"t I Signed and sea led this .l7t .h-ciay of Apx il 1962. 7

(saw

Attest: i STON JOHNSO'N I DAVID L; LADD Attesti g Officer Commissioner of Patents September 26, 1961 CERTIFICATE ,OF CORRECTION Patent Noj- 3,001,29 September 26, 1961 Column 6 lir le 20 after' "by'? strike out "including Signed and s ealed this lTth day of .April 1962..

(SEAL) Attest:

ESTON JOHNSON DAVID L; Attesting Offcer Conmjssioner of Patents 

5. THE METHOD OF BONDING A CERAMIC TO AN ALUMINUM MEMBER WHICH COMPRISES METALLIZING THE SURFACE OF THE CERAMIC WITH A FUSIBLE ALLOY CONSISTING ESSENTIALLY OF 2-10% BY WEIGHT OF A METAL SELECTED FROM THE GROUP CONSISTING OF TITANIUM AND ZIRCONIUM AND COMBINATIONS AND ALLOYS THEREOF; ABOUT 10-85% OF A DUCTILE METAL SELECTED FROM THE GROUP CONSISTING OF LEAD, ZINC, BISMUTH, CADMIUM, INDIUM, AND TIN, AND COMBINATIONS AND ALLOYS THEREOF; AND THE REMAINDER A METAL SELECTED FROM THE GROUP CONSISTING OF COPPER, SILVER AND NICKEL, AND COMBINATIONS AND ALLOYS THEREOF; AND BRAZING THE ALUMINUM MEMBER TO THE FUSIBLE ALLOY THUS BONDED TO THE CERAMIC SURFACE, THEREBY FORMING A TIGHTLY ADHERENT HERMETIC CERAMIC-TO-ALUMINUM SEAL. 